smontanaro 

Thanks for the thread reference. Reading that allowed me to find the serial number sleuthing thread on Tonton Velo with alain2908's spreadsheet. That suggests mine is probably from late '54 or sometime in '55.

Edit: Also jonny7 you should feel lucky yours has its head badge intact. Mine's missing. When I hunted around, I found one on eBay which the seller has listed for around $300!